Welcome onboard.
Suggest you browse the board for specific mods you wish to make since your question is too general to give you specific advice. As others have noted that would be a lot of $$ to put into your car, best you set aside some for unforeseen repairs.
Re CEL on, unless you have had code read it would not be wise to just guess the problem/solution. CEL can come on for many reasons, check FAQ section on home page for list. If you alreadt have the code post in the Troubleshooting Forum for interpretation and probable causes.
Enjoy the ride.
